Resolution of fronts: comparison of ECOSTRESS 70-m scale L2 to GHRSST L2, L3 and L4 products

Presented at the GHRSST XXIII international science team meeting, 27 June-1 July 2022, online and in-person (Barcelona). #GHRSST23

Short abstract

The ECOSTRESS L2 surface temperature pixel scale of 70m provides an opportunity for comparison of gradient intensity and spatial resolution of frontal features observed in GHRSST L2, L3, and L4 products.  We carried out our analysis in the Alboran Sea frontal region of the western Mediterranean because of the intensity of the gradients associated with the basin-wide eddies.  In all of the GHRSST products, gradients were well resolved using the Sobel 3×3 kernel. However, it was not possible to resolve gradients in ECOSTRESS L2 scenes with the Sobel kernel because of the high noise levels, but gradients were resolved with an 11×9 smooth noise robust gradient kernel proposed by Holoborodko.  As expected, SST gradient intensities scaled inversely with both pixel size and the size of the gradient operator.  Spatial position of gradients differed substantially among products, with the best fidelity in L2P products, followed by L3.  L4 products varied in spatial fidelity as a result of the time scale of temporal averaging, and varied in resolution of gradient intensity depending on pixel size. ECOSTRESS, because of its much smaller pixel scale, provides added value to GHRSST products by identifying more precisely the locations and intensities of the steepest gradients.